Metal powder production method and metal powder production device

ABSTRACT

A metal powder production method and a metal powder production device capable of reducing the size of the device, reducing costs, and obtaining spherical metal powder are provided. Supply means supplies a downward flow of molten metal, and a plurality of jet burners emit flame jets to the downward flow of the molten metal supplied from the supply means. Each of the jet burners is provided to emit the flame jet from the same angle and from each of positions rotationally symmetrical with each other with respect to the downward flow of the molten metal.

BACKGROUND OF INVENTION

1. Technical Field

The present invention relates to a metal powder production method and a metal powder production device.

2. Background Art

Conventionally, atomization methods have been widely used for producing metal powder (refer to, for example, MURAKAMI, Yotaro, “Method for producing high-quality metal powder”, (online), September 2003, The New Materials Center, Osaka Science & Technology Center (searched on Jan. 17, 2011), the Internet (URL: http://www.ostec.or.jp/nmc/TOP/nmc_news.htm)). Typical atomization methods include a water atomization method and a gas atomization method that produce powder by emitting a jet of water or gas to molten metal (metal melt), pulverizing the molten metal, and allowing it to be solidified as droplets (refer to, for example, Japanese Unexamined Patent Application Publication Numbers. 2006-63357, 2005-139471, and 2004-183049). In addition, the typical atomization methods also include a disk atomization method that produces the powder by allowing the molten metal to be dropped on a rotating disk, and pulverizing it by applying a shear force in a tangential direction, and a plasma atomization method that allows a fine wire of Ti or the like to become particles by heat of plasma and kinetic energy.

SUMMARY OF INVENTION Technical Problem

However, the water atomization method has the problem of increased equipment costs, because a high-pressure pump for emitting a jet of water at high speed is expensive. In addition, the water atomization method has such a problem that the shape of the produced powder is irregular. The gas atomization method has such a problem that material costs, equipment costs and other costs are high because high-pressure gas production equipment is required in order to use high-pressure gas, and the gas to be used is expensive. The disk atomization method has such a problem that equipment costs are high, because it is necessary to increase a rotation rate of the disk in order to produce the fine metal powder, and such a problem that technology for increasing the rotation rate of the disk has already reached the limit. The plasma atomization method has such a problem that a plasma torch is expensive. In addition, the plasma atomization method also has the problem of an increase in size of the device, because the plasma torch is used.

The present invention is made in view of the above-described problems, and an object of the present invention is to provide a metal powder production method and a metal powder production device capable of reducing the size of the device, reducing the costs, and obtaining spherical metal powder.

Solution to Problem

In order to achieve the above-described object, a metal powder production method according to the present invention obtains metal powder by emitting a flame jet to molten metal or a metal wire.

A metal powder production device according to the present invention includes supply means for supplying molten metal or a metal wire, and a jet burner for emitting a flame jet to the molten metal or the metal wire supplied from the supply means.

It is possible for the metal powder production device of the present invention to preferably implement the metal powder production method according to the present invention. The metal powder production method and the metal powder production device according to the present invention can obtain the metal powder by using the principle of an atomization method. By emitting the high-temperature flame jet to the molten metal, the molten metal can be pulverized. Further, by emitting the high-temperature flame jet to the metal wire, the metal wire is melted and its molten metal can be pulverized. As the temperature of the flame jet at this time is higher than those of high-pressure water of a water atomization method and high-pressure gas of a gas atomization method, flow velocity of blowing fluid can be increased to be higher than those of the water atomization method and the gas atomization method. Due to its high temperature, it is not necessary to cool the molten metal for atomization, nor to increase the temperature of the molten metal more than necessary. Therefore, the molten metal can be finely pulverized. Thus-pulverized molten metal is allowed to fall or scatter in an atmosphere and statically supercooled, so as to enable vitrification and to obtain fine metal powder with ease. In addition, it is possible to obtain the metal powder that is finer than those obtained by the water atomization method and the gas atomization method.

According to the metal powder production method and the metal powder production device of the present invention, it is possible to obtain the spherical metal powder. The jet burners used in the metal powder production method and the metal powder production device according to the present invention are relatively inexpensive and small-sized as compared with a high-pressure pump used in the water atomization method, high-pressure gas production equipment used in the gas atomization method, a plasma torch used in a plasma atomization method and the like, and therefore, it is possible to reduce the size of the device and to reduce the costs including equipment costs, material costs and the like.

It is preferable that the metal powder production method and the metal powder production device of the present invention are configured to be able to emit the flame jet to the molten metal or the metal wire at a speed faster than the speed of sound. In this case, the molten metal can be finely pulverized by a shock wave emitted by the flame jet, and the fine metal powder can be obtained. According to the metal powder production method and the metal powder production device of the present invention, the atomization method to the molten metal or the metal wire may be a free fall type or may be a confined type. According to the metal powder production method and the metal powder production device of the present invention, it is preferable that the flame jet is emitted to obliquely intersect a flow direction of the molten metal or an extending direction of the metal wire. In this case, the fine metal powder can be produced efficiently.

According to the metal powder production method of the present invention, it is preferable that the flame jet is emitted from a periphery of the molten metal or the metal wire so that the flame jet collides against the molten metal or the metal wire with an almost equal jet pressure and without leaving any space along an outer periphery of the molten metal or the metal wire. According to the metal powder production device of the present invention, it is preferable that the jet burner emits the flame jet from a periphery of the molten metal or the metal wire so that the flame jet collides against the molten metal or the metal wire with an almost equal jet pressure and without leaving any space along an outer periphery of the molten metal or the metal wire. This makes it possible to prevent the molten metal or the metal wire from scattering to escape from the flame jet at the position where the flame jet collides against the molten metal or the metal wire. Therefore, the uniform atomization to the molten metal or the metal wire is possible, and the fine and uniform spherical metal powder can be obtained. It is also possible to improve production efficiency of the metal powder.

According to the metal powder production method of the present invention, a circular jet orifice for emitting the flame jet may be provided, and the flame jet may be emitted by arranging the molten metal or the metal wire on an inner side of the flame jet emitted from the jet orifice. According to the metal powder production device of the present invention, the jet burner may include a circular jet orifice for emitting the flame jet, and the molten metal or the metal wire may be arranged on an inner side of the flame jet emitted from the jet orifice. In this case, the flame jet can be made to collide against the molten metal or the metal wire with an almost equal jet pressure and without leaving any space along an outer periphery of the molten metal or the metal wire, with relative ease. One jet burner and one combustion chamber will suffice, and therefore, the size of the device can be reduced further, and the production costs can be reduced.

According to the metal powder production method of the present invention, a plurality of flame jets may be emitted to the molten metal or the metal wire from positions rotationally symmetrical with each other with respect to the molten metal or the metal wire. According to the metal powder production device of the present invention, the jet burner may include a plurality of jet burners and may be provided to emit the flame jets to the molten metal or the metal wire from positions rotationally symmetrical with each other with respect to the molten metal or the metal wire. In this case, it is possible to pulverize the molten metal finely and to obtain the fine metal powder, by collisions between the plurality of flame jets.

Further, when there are plurality of jet burners, each of the jet burners may have an elongated jet orifice for emitting the flame jet, and a major axis direction of the jet orifice may be arranged to correspond to an outer periphery of the molten metal or the metal wire. In this case, the flame jet emitted from the jet orifice of each jet burner can be spread in a plane shape or divided into a plurality of jets, along the major axis direction of the jet orifice. When the flame jets are emitted from the plurality of jet burners so as to surround the molten metal or the metal wire, the uniform atomization to the molten metal or the metal wire is possible. It is preferable that there are three or more jet burners so as to surround the molten metal or the metal wire.

According to the metal powder production device of the present invention, the jet burner may have a heat-resistant nozzle at its tip end, the heat-resistant nozzle having a through hole therein through which the molten metal or the metal wire passes, and the jet burner may be provided to be able to emit the flame jet to the molten metal or the metal wire passing through the through hole. In this case, the metal powder can be obtained by one jet burner. The heat-resistant nozzle may divide the flame jet in its inside into a plurality of jets, and may emit the divided jets to the molten metal or the metal wire, passing through the through hole, from positions rotationally symmetrical with each other. Any material, such as carbon or water-cooled copper, may be used to form the heat-resistant nozzle as long as the material is heat-resistant.

Advantageous Effects of Invention

According to the present invention, it is possible to provide the metal powder production method and the metal powder production device capable of reducing the size of the device, reducing the costs, and obtaining the spherical metal powder.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1( a) and 1(b) are side views illustrating a usage state of a metal powder production device according to a first embodiment of the present invention where (a) shows a free fall type, and (b) shows a confined type;

FIG. 2 is a side view illustrating a modification of the metal powder production device according to the first embodiment of the present invention, in which a metal wire is used;

FIG. 3 is a side view illustrating a modification of the metal powder production device according to the first embodiment of the present invention, in which jet burners are modified;

FIG. 4 is a vertical cross-sectional view illustrating the metal powder production device according to a second embodiment of the present invention;

FIG. 5( a) is a perspective view illustrating the metal powder production device according to a third embodiment of the present invention, and

FIG. 5( b) is a perspective view illustrating its usage state;

FIG. 6( a) is a front view illustrating a jet orifice of the metal powder production device as in FIG. 5, and

FIG. 6( b) is a side view illustrating the shape of an emitted flame jet;

FIG. 7( a) is an enlarged side view illustrating a state of the flame jets emitted from the metal powder production device as in FIG. 1( a),

FIG. 7( b) is an enlarged side view near an emitting position of the flame jet, illustrating a state of atomization when molten metal is used in the metal powder production device as in FIG. 1( a),

FIG. 7( c) is an electron micrograph of Fe₇₅Si₁₀B₁₅ amorphous powder obtained from Fe—Si—B based molten metal by the metal powder production device as in FIG. 1( a), and

FIG. 7( d) is an electron micrograph illustrating enlarged particles of the powder;

FIG. 8( a) is an electron micrograph at 150-fold magnification and

FIG. 8( b) is an electron micrograph at 1000-fold magnification of metal powder obtained by the metal powder production device as in FIG. 2 from a metal wire of stainless steel SUS420;

FIG. 9( a) is an electron micrograph at 1500-fold magnification and

FIG. 9( b) is an electron micrograph at 2500-fold magnification of metal powder obtained by the metal powder production device as in FIG. 2 from a metal wire of a TIG welding rod (TGS50 manufactured by Kobe Steel, Ltd.);

FIG. 10( a) is an electron micrograph at 200-fold magnification and

FIG. 10( b) is an electron micrograph at 1200-fold magnification of metal powder obtained by the metal powder production device as in FIG. 2 from a metal wire of SUS420 alloy; and

FIGS. 11( a) to 11(c) are graphs illustrating particle size distribution of metal powder produced by emitting a flame jet to molten metal of Fe—Si₁₀-B₁₅ alloy by (a) the metal powder production device as in FIG. 1( a), (b) the metal powder production device as in FIG. 4, and (c) the metal powder production device as in FIG. 4 having a Laval nozzle type jet orifice.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 and FIG. 3 illustrate a metal powder production device according to a first embodiment of the present invention.

As illustrated in FIG. 1, a metal powder production device 10 has supply means 11 and a plurality of jet burners 12. In the following, an explanation will be mainly given to a free fall type that is illustrated in FIG. 1( a).

As illustrated in FIG. 1( a), the supply means 11 is formed by a container containing molten metal. The supply means 11 has, at the center of its bottom surface, a molten metal injection nozzle 11 a that communicates with its inside. The supply means 11 is configured to be able to discharge the molten metal contained therein downward from the molten metal injection nozzle 11 a.

Each of the plurality of jet burners 12 is able to emit a flame jet 12 a at a speed faster than the speed of sound. Each of the jet burners 12 is arranged under the supply means 11 to be able to emit the flame jet 12 a obliquely downward. Each of the jet burners 12 is provided to emit the jet to a downward flow 1 of the molten metal from the molten metal injection nozzle 11 a in such a manner that the jet obliquely intersects the downward flow 1 at the same angle, from each of positions rotationally symmetrical with each other with respect to the downward flow 1. Thereby, the respective jet burners 12 are made to emit the flame jets 12 a to one point of the downward flow 1 in a concentrated manner.

According to a specific example, the jet burner 12 is formed by a jet burner manufactured by Hard Industry Yugen Kaisha, which is small-sized, and is able to emit the flame jet 12 a at the speed faster than the speed of sound. There are three jet burners 12 that are arranged at positions with the same distance from the downward flow 1 and at intervals of a central angle of 120 degrees, with the downward flow 1 of the molten metal serving as a central axis, and that emit the jets to the downward flow 1 from an obliquely upward direction at an angle of about 45 degrees. Further, each of the jet burners 12 are made to emit the flame jet 12 a at the same pressure and speed.

It is possible for the metal powder production device 10 to preferably implement a metal powder production method according to the first embodiment of the present invention. The metal powder production device 10 can obtain metal powder by using the principle of an atomization method. By emitting the high-temperature flame jet 12 a to the downward flow 1 of the molten metal, the molten metal can be pulverized. As the temperature of the flame jet 12 a at this time is higher than those of high-pressure water of a water atomization method and high-pressure gas of a gas atomization method, flow velocity of blowing fluid can be increased to be higher than those of the water atomization method and the gas atomization method. Due to its high temperature, it is not necessary to cool the molten metal for atomization, nor to increase the temperature of the molten metal more than necessary. For example, the temperature of the molten metal may be set to be lower than those of the conventional water atomization method and the gas atomization method by about 50 to 100° C. Therefore, the molten metal can be finely pulverized under the condition in which the molten metal is amorphized more easily. Thus-pulverized molten metal is allowed to fall or scatter in an atmosphere and statically supercooled, so as to enable vitrification and to obtain fine metal powder with ease. In addition, it is possible to obtain the metal powder that is finer than those obtained by the water atomization method and the gas atomization method.

When each of jet burners 12 emits the flame jet 12 a at the speed faster than the speed of sound, the metal powder production device 10 can finely pulverize the molten metal by a shock wave emitted by the flame jet 12 a. Further, each of the jet burners 12 emits the flame jet 12 a to one point of the downward flow 1 in a concentrated manner from the same angle and from each of the positions rotationally symmetrical with each other with respect to the downward flow 1 of the molten metal, which makes it possible to pulverize the molten metal more finely and to obtain the finer metal powder, by collisions between the plurality of flame jets 12 a. It should be noted that the obtained metal powder can be collected easily when a container or a chamber is provided under the supply means 11 in such a manner to cover peripheral portions and lower portions of the respective flame jets 12 a.

As the jet burners 12 used in the metal powder production device 10 are relatively inexpensive and small-sized as compared with a high-pressure pump used in the water atomization method, high-pressure gas production equipment used in the gas atomization method, a plasma torch used in a plasma atomization method and the like, it is possible to reduce the size of the device and to reduce the costs including equipment costs, material costs and the like.

Incidentally, the metal powder production device 10 may be a confined type as illustrated in FIG. 1( b). With regard to the confined type, efficient atomization is possible without attenuating kinetic energy of the flame jets 12 a of the respective jet burners 12, as the confined type can supply the molten metal directly to an atomizing zone, as well as the similar effects as those of the free fall type can be obtained. When the conventional gas atomization or the like is used in the confined type, there is such a problem that the molten metal is solidified and clogging of the molten metal injection nozzle 11 a is easily caused as the molten metal injection nozzle 11 a is cooled by the emitted gas and the like. On the contrary, with the metal powder production device 10 as illustrated in FIG. 1( b), it is possible to prevent the solidification of the molten metal and the occurrence of the clogging of the molten metal injection nozzle 11 a because the high-temperature flame jets 12 a are emitted from the respective jet burners 12 and the molten metal injection nozzle 11 a is not cooled.

In the metal powder production device 10, as illustrated in FIG. 2, the supply means 11 may be provided to be able to supply a metal wire 2 continuously to a downward direction, and the respective jet burners 12 may be provided to emit the flame jets 12 a to the metal wire 2. In this case, the high-temperature flame jets 12 a are emitted to the metal wire 2, so as to melt the metal wire 2 and to pulverize the melted metal. Material of the metal wire 2 may be, for example, stainless steel or SUS420 alloy.

Further, the metal powder production device 10 may include one jet burner 12 having a heat-resistant nozzle at its tip end. The heat-resistant nozzle may be configured to include a through hole therein, through which the molten metal or the metal wire passes, divide the flame jet 12 a in its inside into a plurality of jets, and emit the divided jets to the molten metal or the metal wire, passing through the through hole, from positions rotationally symmetrical with each other and from the same angle with respect to the molten metal or the metal wire. In this case, it is possible to obtain the metal powder by one jet burner 12. The heat-resistant nozzle may be obtained by forming the nozzle used in the water atomization method or the gas atomization method by heat-resistant material such as carbon or water-cooled copper.

Further, in the metal powder production device 10, as illustrated in FIG. 3, a jet nozzle 12 c of each of the jet burners 12 may be bent so that an emitting direction of the flame jet 12 a has a specified angle with respect to a longitudinal direction of a body 12 b of the jet burner 12. In this case, the jet nozzle 12 c can be easily brought closer to the molten metal injection nozzle 11 a of the supply means 11. This is effective especially when the metal powder production device 10 is the confined type.

FIG. 4 illustrates the metal powder production device and the metal powder production method according to a second embodiment of the present invention.

As illustrated in FIG. 4, a metal powder production device 20 is the confined type, and has the supply means 11 and the jet burner 12.

Incidentally, in the following explanation, the same numerals and symbols will be used to designate the same components as those in the metal powder production device 10 according to the first embodiment of the present invention, and the repeated explanation will be omitted.

The supply means 11 has a container 21 containing the molten metal, and a supply hole 21 a that communicates with the outside at the center of the bottom of the container 21. Further, the supply means 11 has the molten metal injection nozzle 11 a that communicates with the supply hole 21 a and is attached to the center of the bottom surface of the container 21 via a heat insulating plate 22 (an alumina plate, for example). The molten metal injection nozzle 11 a has a tapered shape, whose tip end has such an external form that is gradually thinnes downward. The supply means 11 can supply the molten metal that is contained in the container 21 through the molten metal injection nozzle 11 a.

The jet burner 12 has a combustion chamber (not illustrated) and a circular jet orifice 24 for emitting the flame jet. The jet burner 12 is provided under the container 21 of the supply means 11 in such a manner that the molten metal injection nozzle 11 a is arranged on an inner side of the jet orifice 24. The jet burner 12 is formed in such a manner that the jet orifice 24 corresponds to the tapered shape of the tip end of the molten metal injection nozzle 11 a.

The jet burner 12 is configured to be able to emit the flame jet from the jet orifice 24 toward a forward inner side and along the circumference of the jet orifice 24 without leaving any space. Thereby, the jet burner 12 is able to emit the flame jet concentrically on one point of the molten metal, from the periphery of the molten metal supplied from the molten metal injection nozzle 11 a, in such a manner that the flame jet obliquely intersects a flow direction of the molten metal. Further, with the jet burner 12, the flame jet is made to collide against the molten metal along the outer periphery of the molten metal supplied from the molten metal injection nozzle 11 a with an almost equal jet pressure and without leaving any space.

The jet burner 12 also has a water cooling unit 25 that circulates water in the periphery of the jet orifice 24 and cools the jet orifice 24. Incidentally, the jet burner 12 can also emit the flame jet at the speed faster than the speed of sound. In the specific example, the jet burner 12 is made to emit the jet to the molten metal supplied downward from the molten metal injection nozzle 11 a, from the obliquely upward direction at an angle of about 40 degrees.

It is possible for the metal powder production device 20 to preferably implement the metal powder production method according to the second embodiment of the present invention. With the metal powder production device 20 and the metal powder production method according to the second embodiment of the present invention, the flame jet that is emitted from the periphery of the molten metal is made to collide against the molten metal along the outer periphery of the molten metal with the almost equal jet pressure and without leaving any space, which makes it possible to prevent the molten metal from scattering to escape from the flame jet at the colliding position. Therefore, uniform atomization to the molten metal is possible, and fine and uniform spherical metal powder can be obtained. It is also possible to improve production efficiency of the metal powder. According to the specific example, the diameter of the produced metal powder is about 5 μm.

With the metal powder production device 20 and the metal powder production method according to the second embodiment of the present invention, one jet burner 12 and one combustion chamber will suffice, and therefore, the size of the device can be reduced further, and the production costs can also be reduced further. Incidentally, it is also possible for the metal powder production device 20 and the metal powder production method according to the second embodiment of the present invention to emit the high-temperature flame jet to the metal wire, not to the molten metal.

FIG. 5 and FIG. 6 illustrate the metal powder production device and the metal powder production method according to a third embodiment of the present invention.

As illustrated in FIG. 5 and FIG. 6, a metal powder production device 30 has the supply means 11 and the jet burners 12.

Incidentally, in the following explanation, the same numerals and symbols will be used to designate the same components as those in the metal powder production device 10 according to the first embodiment of the present invention and the metal powder production device 20 according to the second embodiment of the present invention, and the repeated explanation will be omitted.

In the metal powder production device 30, there are three jet burners 12, each of which has an elongated jet orifice 24 for emitting the flame jet 12 a. Each of the jet burners 12 is arranged in such a manner that a major axis direction of the jet orifice 24 corresponds to the outer periphery of the downward flow 1 of the molten metal. Each of the jet burners 12 is provided to be able to emit the flame jet 12 a at the same pressure and the same speed to the downward flow 1, from each of the positions rotationally symmetrical with each other and from the same angle with respect to the downward flow 1.

In the specific example illustrated in FIG. 5 and FIG. 6, each jet orifice 24 has a gourd shape in which two circles are connected. Further, the respective jet burners 12 are arranged at the positions with the same distance from the downward flow 1 and at the intervals of the central angle of 120 degrees, with the downward flow 1 of the molten metal serving as the central axis, and the respective jet burners 12 emit the jets to the downward flow 1 from the obliquely upward direction at the angle of about 40 degrees.

It is possible for the metal powder production device 30 to preferably implement the metal powder production method according to the third embodiment of the present invention. With the metal powder production device 30 and the metal powder production method according to the third embodiment of the present invention, the flame jet 12 a emitted from the jet orifice 24 of each jet burner 12 can be spread in a plane shape or divided into a plurality of jets, along the major axis direction of the jet orifice 24, as illustrated in FIG. 6( b). Therefore, the flame jets 12 a are emitted from the respective jet burners 12 so as to surround the downward flow 1 of the molten metal, and thus, the flame jets 12 a are made to collide against the downward flow 1 of the molten metal along the outer periphery of the downward flow 1 of the molten metal with the almost equal jet pressure and without leaving any space. This makes it possible to prevent the molten metal from scattering to escape from the flame jet 12 a at the colliding position. Therefore, the uniform atomization to the molten metal is possible, and the fine and uniform spherical metal powder can be obtained. It is also possible to improve the production efficiency of the metal powder.

Incidentally, it is also possible for the metal powder production device 30 and the metal powder production method according to the third embodiment of the present invention to emit the high-temperature flame jets 12 a to the metal wire, not to the molten metal.

Example 1

The state of the flame jets 12 a emitted from the metal powder production device 10 as illustrated in FIG. 1( a) is illustrated in FIG. 7( a). A convergence of the plurality of flame jets can be confirmed as in FIG. 7( a). This metal powder production device 10 was used to emit the flame jets 12 a to Fe—Si—B based molten metal, and then fine spherical Fe₇₅Si₁₀B₁₅ amorphous powder was obtained. FIG. 7( b) to FIG. 7( d) illustrate the state of the flame jet 12 a near the emitting position at this time, and electron micrographs of the obtained powder.

Example 2

The metal powder production device 10 as illustrated in FIG. 2 was used to emit the flame jets 12 a to the metal wire 2 of stainless steel SUS420, and then fine spherical metal powder was obtained. Electron micrographs of the obtained metal powder are illustrated in FIG. 8.

Example 3

The metal powder production device 10 as illustrated in FIG. 2 was used to emit the flame jets 12 a to the metal wire 2 of a TIG welding rod TGS50 (manufactured by Kobe Steel, Ltd.), and then fine and spherical metal powder was obtained. Electron micrographs of the obtained metal powder are illustrated in FIG. 9.

Example 4

The metal powder production device 10 as illustrated in FIG. 2 was used to emit the flame jets 12 a to the metal wire 2 of SUS420 alloy, and then fine and spherical metal powder was obtained. Electron micrographs of the obtained metal powder are illustrated in FIG. 10.

Example 5

The metal powder production device 10 as illustrated in FIG. 1( a), the metal powder production device 20 as illustrated in FIG. 4, and the metal powder production device 20 as illustrated in FIG. 4 having a Laval nozzle type jet orifice 24 were used to emit the flame jets to the molten metal of Fe—Si₁₀-B₁₅ alloy, so as to produce the metal powder. Particle size distribution of the metal powder produced in the respective devices is illustrated in FIG. 11.

Incidentally, in the metal powder production device 10 as illustrated in FIG. 1( a), the four jet burners 12 were arranged at the intervals of the central angle of 90 degrees, with the downward flow 1 of the molten metal serving as the central axis, and the respective jet burners 12 emitted the flame jets to the downward flow 1 from the obliquely upward direction at the angle of about 15 degrees (vertex angle of 30 degrees). With regard to combustion parameters per one jet burner 12, air volume is 700 L/min and fuel (kerosene) is 130 mL/min. With regard to the combustion parameters of the metal powder production device 20 as illustrated in FIG. 4, the air volume is 3000 L/min and the fuel (kerosene) is 550 mL/min. With regard to the combustion parameters of the Laval nozzle type, the air volume is 3000 L/min and the fuel (kerosene) is 550 mL/min.

With regard to the metal powder produced by the metal powder production device 10 as illustrated in FIG. 1( a) and by the metal powder production device 20 as illustrated in FIG. 4, the most common diameter was 40 to 70 μm, and the diameter was 100 μm or less for the most part, as illustrated in FIGS. 11( a) and 11(b). With regard to the metal powder produced by the Laval nozzle type, the diameter was 50 μm or less for the most part. From these results, it was confirmed that the fine powder can be obtained by the emission of the flame jet. As the diameter of the produced metal powder is smaller in the Laval nozzle type, it is found that the diameter of the produced metal powder is reduced as the speed of the flame jet is increased.

REFERENCE SIGNS LIST

-   1 downward flow -   2 metal wire -   10 metal powder production device -   11 supply means -   11(a) molten metal injection nozzle -   12 jet burner -   12 a flame jet 

1. A metal powder production method for obtaining metal powder by using a principle of an atomization method, the metal powder production method comprising the steps of: providing a circular jet orifice for emitting a flame jet; arranging molten metal or a metal wire on an inner side of the flame jet emitted from the jet orifice; and emitting the flame jet to the molten metal or the metal wire so as to obtain the metal powder.
 2. The metal powder production method according to claim 1, wherein the flame jet is emitted from a periphery of the molten metal or the metal wire so that the flame jet collides against the molten metal or the metal wire with an almost equal jet pressure and without leaving any space along an outer periphery of the molten metal or the metal wire. 3-4. (canceled)
 5. A metal powder production device for obtaining metal powder by using a principle of an atomization method, the metal powder production device comprising: supply means for supplying molten metal or a metal wire; and a jet burner for emitting a flame jet to the molten metal or the metal wire supplied from the supply means, wherein the jet burner comprises a circular jet orifice for emitting the flame jet, and the molten metal or the metal wire is arranged on an inner side of the flame jet emitted from the jet orifice.
 6. The metal powder production device according to claim 5, wherein the jet burner emits the flame jet from a periphery of the molten metal or the metal wire so that the flame jet collides against the molten metal or the metal wire with an almost equal jet pressure and without leaving any space along an outer periphery of the molten metal or the metal wire. 7-10. (canceled)
 11. The metal powder production method according to claim 1, wherein the jet orifice comprises a Laval nozzle type.
 12. The metal powder production device according to claim 5, wherein the jet orifice comprises a Laval nozzle type.
 13. The metal powder production method according to claim 2, wherein the jet orifice comprises a Laval nozzle type.
 14. The metal powder production device according to claim 6, wherein the jet orifice comprises a Laval nozzle type. 